During a number of interventional procedures related to cardiac treatment, a physician manipulates catheters and/or leads inside the heart chambers and associated vasculature. Two such cardiac procedures include the treatment of an arrhythmia (such as atrial fibrillation) and cardiac pacing. Atrial fibrillation, which refers to an arrhythmia in which the atria (upper chambers of the heart) stop contracting as they fibrillate, is the most commonly experienced heart rhythm abnormality. Both treatment procedures involve directing a catheter or other intravascular device to designated areas in or about the chambers of the heart. For example, an arrhythmia treatment procedure may include directing an ablation device through a blood vessel leading to the heart for subsequent treatment of portions of an atrial wall where the problematic tissue is located. Biventricular pacing also involves the routing and positioning of one or more intravascular devices in proximity to specific locations of the heart, such as the coronary ostium.
A common technique facilitating or easing the directing and placement of the selected medical devices within the heart involves fluoroscopic imaging. However, numerous factors render current approaches using current fluoroscopically guided techniques somewhat cumbersome and lengthy for arrhythmia treatment, such as inadequate three-dimensional reconstruction of the left atrium using some currently available technologies, the inability of the physician to visualize particular tissue sites (such as the pulmonary vein ostia), the varying size of the pulmonary veins and thus the pulmonary vein ostia, the difficulty in keeping the selected medical devices stable at the pulmonary vein ostia and other important sites in the left atrium due to the complex geometry of these areas.
Similar difficulties are present for placing cardiac leads or other diagnostic and therapeutic devices within the coronary sinus. The anatomical structures in and around the coronary sinus itself are not depicted very well by typical fluoroscopic systems since they do not present sufficient contrast to the surrounding anatomical structures. Moreover, cannulating the coronary sinus may be challenging as a result of an enlarged right atrium, rotation of the heart, or presence of a Thebesian valve (a valve close to the opening of the coronary sinus), and coronary sinus stenosis (occlusion) has also been reported in patients with prior coronary artery bypass surgery, further complicating the intended treatment procedure.
The difficulties described above may result in extended times to complete a designated procedure and potentially expose patients to undesired risks associated with such prolonged procedures. In view of such limitations and difficulties, there remains a need in the art for improved methods and apparatus for expeditiously directing and placing medical devices in and around the heart for subsequent diagnosis or treatment.